There are a handful of integration docs that instruct users to create
a bot and select the "Generic bot" type without using a helper macro.
Adds a new macro to replace these instructions, including a screenshot
of the latest UI for selecting a bot type.
Both the integrations use our new Matrix integration (with only one
additional paragraph for the IRC docs), so docs for both should point
to the same underlying Markdown macro for configuring a Matrix bridge.
This is a follow-up to #9491.
The big changes here are:
* Making the install instructions easier to copy/paste.
* Adding numbering for the IRc integration. We probably want to do a
similar thing with Matrix, too.